Chemistry is the science of interacting particles and the various states of matter. Developing a better understanding of the atomic model through experiments with gases, scientists discovered the Ideal Gas Law, developed phase diagrams, and learned about the properties of supercritical fluids. Today's chemists are exploring new ways to control the interactions of atoms, with the goal of making better hydrogen-powered cars and new technologies for the long-term, underground storage of carbon dioxide to reduce greenhouse warming. Part of the series Chemistry: Challenges And Solutions.